Operating Systems

1. Operating Systems MCC – CIS105

2. Topics • Describe the functions of an operating system (OS) • Describe the components of a personal computer operating system • Describe various operating system user interfaces • Describe the OS Management Functions • Describe the differences among multiprocessing, multiprogramming, and time-sharing • List several functions that are typically performed by utility programs CIS 105 – Mesa Community College

3. Operating Systems for Personal Computers • Common Operating Systems • MS-DOS • Windows • MAC OS • Unix • Linux CIS 105 – Mesa Community College

4. Platform • Platform is the combination of the operating system software and computer hardware. • Windows on an Intel-based or AMD-based PC • Wintel is one of the most common • Linux on an Intel-based or AMD-based PC • Mac OS on Intel-based or Freescale-based CIS 105 – Mesa Community College

5. Operating Systems Roles & Components • System software controls the operations of computer hardware. • Serves as the interface between the user, applications, and hardware. • User Interface – how users issue commands to the system. • Primary components (covered in next few slides): • Kernel – core software • Device Drivers – little programs to operate specific hardware • Utility programs – applications used to manage and secure a computer CIS 105 – Mesa Community College

6. Utility Programs Examples CIS 105 – Mesa Community College • File manager • Create, rename, delete, and move files and folders • Backup and Restore • Backup: make copies of files on hard disks to another storage device • Restore: retrieve files from backup device • Use System Restore under Accessories to backup system settings before installing new programs. • Control Panel Items • Add and Remove Programs • Date and Time • Virus Protection and Firewalls • Power Options

7. Device Drivers • Device drivers are little programs used to operate a particular device. • The programs are provided by the manufactures. • Device drivers must be installed after installing the new hardware, or the device will not work. • Some common devices that require drivers are the mouse, keyboard, video display card, printer, scanner, and USB ports. CIS 105 – Mesa Community College

8. Kernel • Main part (core) of the operating system • Loaded from hard drive into memory when computer is booted • Cold Boot - starting the computer by turning on the power • Warm Boot – restarting the computer when it is already on • Resides in memory after it has been loaded(resident portion or the core) • Loads other operating system programs from disk storage as needed (nonresident) CIS 105 – Mesa Community College

9. Boot Process • Central Processing Unit (CPU) reads the chip with the BIOS (Basic Input/Output System) • POST – Power On Self Test • Tests memory, buses, cards, etc • Results are compared to CMOS values • Load Boot Program from hard drive • Boot program loads Kernel from hard drive • User’s system configuration is loaded • Reads preference files and registry • Load required device drivers • Present User Interface CIS 105 – Mesa Community College

10. User Interface – how users issue commands to the system. Command-Line (see next slide for examples) Dos, Unix Menu-driven DosShell List of commands presented Graphical User Interface (GUI) Interact with icons, menus, buttons, etc. Windows, Mac OS, Linux Win CE – handhelds, palmtops User Interfaces CIS 105 – Mesa Community College

11. User Interfaces - examples CIS 105 – Mesa Community College

12. OS Management Functions • Process Management (program or task) • Memory Management • Input/output Management • System Administration • See next few slides for additional information… CIS 105 – Mesa Community College

13. Process or Task Management • The OS determines which instructions the processor (CPU) will execute. • A processor can only do one thing at-a-time, but it pretends to do more than one thing by… • Multiprogramming - is running two or more programs concurrently, but only one is actually being executed at any one time. • Programs take turns using the CPU • Event-driven – An event tells the operating system when to switch, for example a button click could suspend a file download in background. • Time-Sharing - programs take turns using the CPU • Time-driven – preset time intervals • Typically used in mainframes with many users • Multiprocessing – is running multiple programs simultaneously in a system with more than one CPU • Each programs runs on its own processor (dual core) CIS 105 – Mesa Community College

14. Memory Management • The OS allocates memory (RAM) to each application as it is launched or started. • Foreground – the program that is currently running • Background – lower priority and waiting for idle time • Virtual Memory • Some computers do not have enough real memory (RAM) to keep all of the programs that are opened loaded in memory. • Portions of programs being executed are stored on disk and are swapped into memory as needed • Can be implemented by paging • Paging • Divide memory into small, fixed-size pages, and pages are saved out to disk when not in use. • If CPU spends too much time paging, it is call thrashing. • To correct thrashing, fewer programs should be ran concurrently, or add additional memory. CIS 105 – Mesa Community College

15. Input / Output Management • The OS handles all I/O to and from storage devices, keyboards, and displays. • Devices installed on each computer may be different, so the OS uses device drivers. • Plug-and-Play – devices have software encoded on them (ROM), which allows them to be recognized by the OS when installed, so the device driver installation process can begin automatically. • Disk and File Management – Format command, copy, delete, rename, etc. (Windows Explorer) CIS 105 – Mesa Community College

16. I/O Management - Printing • Spooling: program saves output to a disk file rather than sending directly to a printer • After saving the file, it is placed in a queue • File printed when printer becomes available • Allows program to complete print command much more quickly, so the user may continue working on the document. • Writing to disk much quicker than sending data to printer CIS 105 – Mesa Community College

17. System Administration • System Performance – use system monitoring software to see which tasks are taking too much time (Ctrl-Alt-Del – Windows Task Manager) • System Security • create users and passwords • Handles network functions • Establishes connections and manages peer-to-peer networks. • Share documents and resources (hard drives, printers) over network. • Network Operating System (NOS) • Usually used to referred to the software on a server dedicated to managing users, services, and security. • Accessibility / Adaptive Technology CIS 105 – Mesa Community College

18. MCC Courses • Learn more about a specific operating system by taking one of the following… • CIS126DL – Linux Operating System • MST150 – MS Windows Professional CIS 105 – Mesa Community College

19. Sources • Capron; Computers: Tools for An Information Age, 8th Ed. 2003 • Pfaffenberger: Computers in Your Future 2003 • Shelly: Discovering Computers 2008 • Microsoft Clipart • Webopedia CIS 105 – Mesa Community College